This is a randomized, placebo-controlled study to assess the efficacy and safety of a pharmaceutical agent, SP303, in the treatment of AIDS-related diarrhea. SP303 (Provir) is derived from a plant species which has been widely used in folk medicine for the treatment of a variety of ailments including diarrhea. The diarrhea associated with AIDS may have multiple etiologies, but infectious causes have been identified in 50-85% of cases. Medications may also be a causative factor. Regardless of etiology, symptomatic treatment of diarrhea in AIDS patients is important for both quality of life and nutritional concerns. Clinical and empirical evidence suggest that AIDS-associated diarrhea may result from excessive secretion of ions. It may therefore be treated by agents designed to inhibit small bowel ion secretion. The study drug has been demonstrated to inhibit chloride ion secretion by intestinal epithelial cells and thus is a logical therapeutic candidate for the treatment of this disorder.